结合使用Blobstore API和Google Cloud Storage-http 404错误消息

Question

Today if an url is incorrect, users get this display from my appengine instance:

Error: Server Error

The server encountered an error and could not complete your request.
Please try again in 30 seconds.

I found this reference on how to address with a proper 404 message using the blobstore.get, but unfortunately it's not working. I figured out why. The bkey always returns some value, so it will always think "its not a invalid bkey". What I'm trying to figure out is how to write the code in the case that the bkey is invalid. Below is my code:

gs_filename = '/gs/%s/%s' % (settings.BUCKET, filename)
bkey = blobstore.create_gs_key(gs_filename)

if not blobstore.get(key):
   logging.info("I got a 404 error'")
else:
  return blobstore_dh.send_blob(bkey, content_type=ct)

Does anyone have any suggestions?

Answer 1

I just ran into this as well and came up with a quick workaround:

from google.appengine.api.blobstore import BlobNotFoundError

..

    try:
        blobstore.BlobReader(blob_key).read(1)
    except BlobNotFoundError:
        logging.info('BlobNotFoundError')
        self.abort(404)

Does feel a bit hackish, so if anybody finds a better way, I would love to hear about it!